JPH0432692B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a diffusion dialysis method using a tubular ion exchange membrane, and is particularly suitable for efficient diffusion dialysis of solutions containing a large amount of suspended solids or solutions that precipitate poorly soluble substances during dialysis treatment. Provides a dialysis method. Conventionally, a diffusion dialysis method using an anion exchange membrane or a cation exchange membrane is known as a method for selectively separating acids or alkalis from solutions containing acids or alkalis. In particular, acid recovery processes using anion exchange membranes not only have many advantages, such as high acid recovery rates, simple processes, and easy operation management, but are also economically viable. Because of its excellent properties, it is widely used industrially, for example, in the treatment of steel pickling liquid, pickling waste liquid, battery waste acid, etc. The above-mentioned processing solution often contains a large amount of suspended solids (hereinafter abbreviated as SS). For example, a steel pickling solution usually contains several hundred ppm to several thousand ppm. Contains SS. Therefore,
After pretreatment such as sedimentation separation, coagulation sedimentation, or filtration is performed to remove the SS content, it is supplied to a dialysis machine and the acid is recovered, but even after these treatments, a sufficiently clear solution cannot be economically produced. Therefore, some SS is supplied to the dialysis machine. A solution containing such an SS component is diffused using a conventionally used so-called filter press type diffusion dialysis device in which many planar ion exchange membranes are stacked or a hollow fiber type diffusion dialysis device in which ion exchange hollow fibers are bundled. Various problems arise when performing dialysis treatment. For example, when a filter press type diffusion dialysis device is used, it is inevitable that SS components will adhere to the channels, spacers, flow plates, ion exchange membrane surfaces, etc. inside the device, and once the SS components have adhered, I almost never leave. Furthermore, even in a hollow fiber type dialysis device using a bundle of ion-exchangeable hollow fibers, clogging due to adhesion of SS components in the channel within the device or on the surface of the fibers was unavoidable. In this way, the SS content in the solution gradually adheres and accumulates on the flow path, spacer, flow plate, or ion exchange membrane surface of a filter press type diffusion dialysis device, or on the flow path and hollow fiber surface of a hollow fiber type dialysis device. This not only increases the dialysis pressure drop and impedes the uniform flow of the solution, but also reduces the recovery rate of acid or alkali, and eventually causes various problems such as scale troubles due to concentration polarization, which can lead to long-term problems. Stable operation becomes impossible. In particular, in filter press type dialysis equipment, if SS content adheres to the spacer, flow plate, or ion exchange membrane surface, even if it is only a small amount, the flow resistance will increase significantly, and the recovery rate of acid or alkali will increase. The above-mentioned problem becomes conspicuous because of the sudden decrease in When this happens, dialysis work is temporarily interrupted and the clogged dialysis machine is disassembled, cleaned, and reassembled to restore its performance, but filter press machines are extremely inconvenient to assemble and disassemble. Therefore, not only does it require a great deal of labor and time, but if handled incorrectly during demolition work,
Expensive ion exchange membranes are subject to physical deterioration such as cracks and pinholes. Furthermore, frequent disassembly and cleaning will reduce the operating rate of the equipment, resulting in a very large loss. On the other hand, in the hollow-eye dialysis machine,
Performance deteriorates more easily than filter press type dialysis equipment due to SS content, and since it is a fiber bundle, it is extremely difficult to restore performance by disassembling and cleaning.
Once clogged with SS, the expensive hollow fiber bundles in the module must be warped and replaced with new ones, which not only prevents stable operation but also causes a huge economic loss. In addition, even if the solution does not contain suspended solids, if the solution is one in which poorly soluble substances are precipitated due to changes in dialysis conditions during dialysis treatment, the above SS content may be added to the dialysis machine. Various adverse effects due to adhesion cannot be avoided, and dialysis treatment itself may not be possible in some cases. In view of the above problems, the present inventors have discovered that when performing dialysis treatment on a solution such as that described above, there is no need to perform sophisticated and complicated pretreatments such as filtration of the solution, coagulation and precipitation prior to dialysis treatment, and The purpose of the present invention is to provide a diffusion dialysis method that can be operated efficiently and stably continuously for a long period of time even when using a solution in which poorly soluble substances are precipitated. That is, in the present invention, a diffusion liquid or a dialysing liquid is present inside an upright tubular ion exchange membrane, and a dialysing liquid or a diffusion liquid is present outside the tubular ion exchange membrane,
This is a diffusion dialysis method characterized by flowing a diffusion liquid and a dialysate in countercurrent flow, and by allowing air bubbles to exist in the dialysate. In particular, in a diffusion dialysis apparatus having a diffusion chamber and a dialysis chamber separated by an upright tubular ion exchange membrane, the flow of the liquid supplied to the diffusion chamber is made into a downward flow, and the flow of the liquid supplied to the dialysis chamber is made into an upward flow. , and a method in which air bubbles are present in the dialysate is particularly preferred because the effects of the present invention are significant. According to the present invention, the diameter of the tubular ion exchange membrane can be selected depending on the SS content and properties of the dialysate (undiluted solution) used, and the spacers, flow plates, etc. used in the filter press type can also be selected depending on the structure. Since there is no need for a lot of water, there is less clogging and there is no need to clean the membrane surface.
SS content is difficult to adhere to. In addition, the pipe diameter and the pitch between the membranes are larger than the hollow fiber type, so there is less clogging due to SS components, and performance deterioration due to concentration polarization is reduced. Furthermore, the SS components adhering to the membrane surface are efficiently removed by the liquid disturbance effect caused by the presence of air bubbles in the dialysate. Therefore, it is possible to stably maintain high dialysis performance over a long period of time. The effects of the present invention were obtained for the first time as a result of detailed studies on the relationship between the shape and arrangement of tubular ion exchange membranes, and the shape and amount of bubbles in dialysate. Alternatively, even if air bubbles are present in the dialysate using a conventional filter press type or hollow fiber type dialysis device, the effects of the present invention cannot be obtained. For example, a filter press type dialysis device has a spacer and a flow distribution plate, and in order to facilitate the assembly work, the spacer and flow distribution plate are in close contact with the ion exchange membrane. Even if air bubbles are present in the device, the effects of the present invention cannot be achieved because the air bubbles remain within the device, particularly within the mesh of the spacer. Note that the technique of creating air bubbles in a dialysis device has conventionally been carried out in a filter press type electrodialysis device. However, the flow rate of the dialysate in diffusion dialysis is generally 1 to 10 cm/min, which is extremely slow compared to that in electrodialysis (1 to 10 cm/sec), or the operating method is different between electrodialysis and diffusion dialysis. It is not possible to obtain the same effect simply by allowing bubbles to exist, for example, because the bubbles are different. In addition, in hollow-eye dialysis equipment,
In order to increase the membrane area per unit volume even if bubbles are present as in the present invention, in other words, the single fiber thickness is thinner and densely packed than in the present invention, so SS adhered to the membrane surface. Removal of minutes is almost impossible. On the other hand, if no air bubbles are present in the dialysate, stable operation over a long period of time is impossible for any type of dialysis apparatus because the air bubbles do not provide the cleaning effect. When carrying out the present invention, the dialysate and the diffusion liquid are preferably brought into countercurrent contact, with the dialysate flowing upward and the diffusion liquid flowing downward, in order to increase the dialysis efficiency due to the concentration gradient. In addition, in the case of dialysis treatment for the purpose of acid recovery,
The flow rate of dialysate is 0.5 to 3/Hr per unit membrane area.
The flow rate ratio of dialysate and diffusion liquid is preferably within the range of
It is preferably within the range of 0.5 to 2.0. According to the invention,
As long as the membrane performance is the same, the dialysate can be treated with the same membrane area and under the same dialysis conditions regardless of the membrane shape.
This means that, for example, when changing a filter press type dialysis device to the dialysis device of the present invention, only the dialysis device of the present invention can be changed without completely changing the specifications of the pump, tank, etc. attached to the filter press type dialysis device. It means that a goal can be achieved by exchanging it for something else, and it is of great industrial significance. Hereinafter, the diffusion dialysis method of the present invention will be explained in detail with reference to the drawings. The diffusion dialysis device used in the present invention is similar to a shell and tube type used in heat exchangers and the like. That is, the diffusion chamber and the dialysis chamber are formed separately through an upright tubular ion exchange membrane. As a typical embodiment, for example, a vertical cylindrical container 1 made of metal or synthetic resin as shown in FIGS. 1 and 2 has three partitions 3, 3', and 3'', and the partition chamber 3 at both ends communicates with 3° through the tubular ion exchange membrane 4. In other words, in the case of FIG. Another part of the chamber represents a dialysis chamber, where the tubular ion exchange membrane 4 is joined to the holes in the tube plates 2 and 2', and the joint 6 is connected to the liquid flowing outside the tubular ion exchange membrane 4. It is necessary to connect the liquid flowing inside to prevent mixing due to leakage.Furthermore, in the above device, the liquid is supplied to and discharged from the central partition 3' and the partitions 3 and 3'' at both ends. Supply ports 8, 9 and discharge ports 7, 10 are provided for this purpose. With the above device, the diffusion liquid (generally water or a dilute solution of an acid or alkali) and the dialysate (undiluted solution) are caused to flow countercurrently and brought into contact with each other through the upright ion exchange membrane 4. In the present invention, the dialysate It is preferable to make countercurrent contact with the dialysate as an upward flow and the diffusion liquid as a downward flow.If the dialysate is a downward flow and the diffusion liquid is an upward flow, the recovery rate of acid or alkali can be increased and efficient separation can be achieved. It is not practical because the equipment and operations are complicated. Although FIG. 1 shows an embodiment in which the diagonally shaded area is the diffusion chamber, either the inside or outside of the tubular ion exchange membrane may be used as the dialysis chamber. For example, if the dialysate is to flow outside the tube, contrary to FIG.
After supplying the diffusion liquid from 0 and bringing it into countercurrent contact through the ion exchange membrane 4, the dialysate is discharged from the discharge port 8, and the diffusion liquid is discharged from the discharge port 9. The present invention requires the use of an ion exchange membrane. Ion exchange membranes are essential when performing diffusion dialysis because they allow acids or alkalis to be separated selectively and at an increased rate. Regarding the type of ion exchange membrane used, an anion exchange membrane is used for separating acids and salts, and a cation exchange membrane is used for separating bases and salts, depending on the purpose. These cation or anion exchange membranes are not particularly limited, and commercially available ones can generally be used. That is, anion exchange membranes include those produced by chloroalkylation, amination, and quaternization of a copolymer of vinylpyridine and divinylbenzene or a copolymer of styrene and divinylbenzene. Further, the cation exchange membrane can be obtained by sulfonation of a copolymer of styrene and divinylbenzene. Of course, it is preferable that these ion-exchange membranes are so-called stiff membranes that are backed by suitable fibers. The ion exchange capacity used is usually 0.1 to 10 milliequivalents/dry resin, which is within the range normally used for dialysis. The use of a tubular ion exchange membrane in the present invention is important in preventing the adhesion of SS components and maintaining stable dialysis performance due to air bubbles, which will be described later. The dimensions of the tubular ion exchange membrane are appropriately selected depending on the type of dialysate, processing capacity, etc., but generally the inner diameter is 0.2 to 10 cm and the length is 5 to 300 cm, particularly the inner diameter is 0.5 to 4 cm and the length is 10 to 300 cm. A length of 200 cm is preferably used. If the inner diameter of the tubular ion exchange membrane is too small, the pressure loss of the solution flowing through the membrane will be large, and when dialysate is passed through the membrane, the SS content will easily clog, and the effect of air bubbles, which will be described later, will be lost. On the other hand, if the inner diameter is too large, the membrane area per unit volume will decrease, making it necessary to increase the size of the device, leading to increased equipment costs and operating costs. Furthermore, if the length of the tubular ion exchange membrane is too short, the acid recovery rate per pass will be low, which will require an increase in the number of membranes and the need to connect them in multiple stages, resulting in inconveniences in process design. On the other hand, if it is too long,
This is not preferable because it causes the same adverse effects as when the pipe diameter is made smaller. The cross-sectional shape of the tubular ion-exchange membrane may be circular, triangular, square, polygonal, etc., but circular is particularly preferred from the viewpoint of ease of membrane formation, ease of membrane handling, and device fabrication. The method of manufacturing the tubular ion exchange membrane is also not limited. For example, a planar ion-exchange membrane is rolled into a tubular shape, and the overlapping surfaces are bonded by heat-sealing, adhesive, sealant, double-sided adhesive, etc.; An embodiment in which a braided tube or a porous tube consisting of the Examples include an embodiment in which ion exchange resin is filled into the pores of the ion exchange resin. The number of tubular ion-exchange membranes and their arrangement with respect to the tube plate are appropriately selected depending on the type of solution, throughput, acid recovery rate, etc., but the tubular membranes are arranged so that they do not come into contact with each other. For example, the arrangement of the tubular ion exchange membranes may be square or equilateral with respect to the tube plate, and the number of tubular ion exchange membranes may be
From the viewpoint of process design, manufacturing, maintenance, etc., it is preferable that the cross-sectional area of the cylindrical container be 5 to 70%. There are also methods for joining the tubular ion-exchange membrane to the holes in the tubesheet, such as joining the tubular ion-exchange membrane directly to the outside of the holes in the tubesheet with an adhesive or sealant, or cutting screws into the holes in the tubesheet. There are methods such as tightening with nuts through packing inserted into the holes in the tube plate, but especially in diffusion dialysis, the amount supplied per unit membrane area is generally
The pressure difference between the dialysate and the diffusion liquid is very small, which is as low as 0.5 to 3/ ^Hm2 , and there is no flow plate or spacer, making joining using the tubular ion exchange membrane extremely simple. The most significant feature of the present invention is that diffusion dialysis is performed while bubbles are present in the dialysate. According to the present invention, by allowing air bubbles to exist in the rising dialysate, the dialysate containing the air bubbles (bubbles group) rises in a meandering manner, and its stirring effect removes the SS adhering to the membrane surface. It can be removed efficiently. Therefore, the presence of air bubbles in the present invention means the presence of air bubbles forcibly blown in from the outside, rather than simply gas accompanying diffusion dialysis. There are no particular restrictions on the method for creating air bubbles in the dialysate. For example, as shown in Figures 1 and 2,
A method in which an aeration pipe 11 or the like is provided in the lower end partition 3 of the dialysis machine, and gas is blown into the dialysate using the aeration pipe, or a method in which the dialysate is stirred while applying high shear force in an external tank, etc. There is a method of supplying a dialysate in which air bubbles are made to exist in advance to a diffusion dialysis device by, for example, introducing gas at high speed. In either method, the amount of bubbles supplied is important in order to exhibit the effects of the present invention, and it is generally preferable to appropriately select the linear velocity relative to the liquid containing gas from 0.1 to 10 m/min. If the linear velocity is too low, the cleaning effect due to bubbles will not be sufficient, and if it is too high, not only will the operating efficiency decrease, but also a sufficient cleaning effect will not be obtained. Diffuser pipe 11 used for blowing the above gas
is provided with an air diffuser hole 12 for blowing gas into the liquid, and the gas blown through the air diffuser pipe is separated into gas and liquid in the upper partition chamber 3'', and is exhausted to the outside of the apparatus through the gas vent 13. Diffusion pipe 11
Porous or mesh-like pipes made of synthetic resin, metal, ceramic, etc., or pipes with many holes drilled on the side of the pipe are used, but in either case, the gas can be uniformly distributed over the entire length of the pipe. gush,
It is preferable to use one that can evenly supply gas to the tubular ion exchange membrane group. The gas can be blown into the air diffuser continuously or intermittently, and in the case of the latter, it can be done regularly or irregularly. In either case, it is determined as appropriate based on the properties and amount of SS in the dialysate, the structure of the dialysis device, dialysis conditions, the amount of SS attached to the membrane surface, etc. Normally, it is sufficient to blow for 1 to 30 minutes once every 1 to 100 hours. In the present invention, it is possible to adopt either a mode in which the dialysate is supplied inside the tubular ion exchange membrane (tube side) or a mode in which the dialysate is supplied outside the tubular ion exchange membrane (shell side). The method to be adopted is appropriately selected depending on the properties of the dialysate, the structure of the dialysis apparatus, etc. In either case, it is important to have air bubbles present in the dialysate, and when air bubbles are present in the diffusion liquid, a slight effect can be expected compared to the case where no air bubbles are present. It is difficult to achieve the same effect. In addition, the material, shape, construction method, etc. of each part of the device used in the present invention may be appropriately selected within a range that satisfies the above requirements. As for the gas, inert gases such as air and nitrogen are generally used, and air is most preferably used. As can be understood from the above explanation, according to the present invention, there is no need for the advanced pretreatment performed in the conventional filter press type or hollow fiber type, and the dialysis fluid can be absorbed into the dialysate by the reaction during the dialysis treatment. Even if it produces poorly soluble precipitates or crystals,
Continuous operation is possible in a stable condition for a long period of time.
Therefore, it is an advantageous dialysis method that requires less expense for stopping, dismantling, and cleaning the dialysis equipment.
Furthermore, it brings about immeasurable effects, such as making the operation and management of the dialysis machine extremely easy. Examples of the present invention will be shown below. Example 1 Steel waste acid containing sulfuric acid has a SS content of silica, carbon, etc. from 500 to 500 as the scale content on the steel surface.
Contains a very large amount of 2000ppm. When carrying out diffusion dialysis of the waste acid, a filter press type dialysis device and
A comparison was made between a dialysis method using a hollow fiber type dialysis device and the dialysis method of the present invention. The specifications of the three types of dialysis machines used are shown below.
Both have the same membrane area. Filter press type dialysis device 62 pairs of anion exchange membranes are stacked alternately via gaskets and spacers to form a stack, and a liquid supply frame/tightening frame is placed at both ends of the stack and tightened with tightening bolts to form a diffusion dialysis device. did. Effective membrane area Width 20cm x length 50cm Number of dialysis rooms Dialysis rooms 63 rooms Diffusion rooms 62 rooms Total effective membrane area 6.2m ² Gasket thickness, material Dialysis room 2mm (Neoprene, etc.) Diffusion room 1mm (Neoprene, etc.) Ion exchange membrane Manufactured by Tokuyama Soda Co., Ltd. Neopceta AFN (product name) Spacer Polyethylene diagonal mesh Hollow fiber type dialysis device Anion-exchange hollow fibers are bundled with the openings at both ends aligned, and each opening at both ends is tied together using adhesive. A group of hollow fibers that were glued together with the fiber hollow portions left open was housed in a cylindrical container to construct a hollow fiber type diffusion dialysis device. Hollow fiber dimensions: Outer diameter: 0.5 mm x inner diameter: 0.3 mm Effective membrane area: 6.2 m Dimensions of ² cylindrical containers: Outer diameter: 200 mm x length: 450 mm The tubular dialysis device of the present invention has the same structure as the hollow fiber dialysis device described above, but The tubular membrane used has an inner diameter of 10
The membranes were arranged in a square array with a pitch of 15 mm. Shape and dimensions of tubular ion exchange membranes Cross section; Circular dimensions; Inner diameter 10 mm x Length 1000 mm x Thickness 0.15 mm Number of tubes: 196 Main tubular membrane arrangement Arrangement; Square pitch; 15 mm Dimensions of the dialysis machine body Dimensions: Width 230 mm ×Depth 230
mm x height 1300 mm Effective membrane area 6.2 m ² The operating method and dialysis conditions of the above dialysis machine are as follows.

[Table] The temperature of both the dialysate and the diffusion liquid was adjusted to 25°C, and they were continuously supplied to the dialysis machine using a one-time process and then discharged from the system. In addition, each device was equipped with piping for supplying air to the dialysate inside the device. That is, in the filter press type dialysis apparatus, an air supply pipe is provided immediately before the inlet of the liquid supply frame that supplies the dialysate. In the hollow fiber type dialysis device, air supply pipes were provided at eight locations around the outer periphery of the lower part of the central partition of the cylindrical container.
In the tubular dialysis apparatus of the present invention, the ion exchange membranes are uniformly distributed and supplied through the perforated plate provided in the lower end partition. The air supply was periodically and intermittently for 5 minutes every 12 hours, and the supply was at a superficial linear velocity of 1 m/min. A waste acid recovery experiment was conducted using the above equipment and dialysis conditions, and the acid recovery rate and the change in dialysis chamber inlet pressure over time were first investigated.
Shown in the table. Note that the acid recovery rate was determined using the following formula. Recovery rate = acid concentration in the diffusion liquid x volume of the diffusion liquid / acid concentration in the dialysate x volume of the dialysate

[Table] * indicates a comparative example.
In filter press type and hollow fiber type dialysis machines, if dialysate with a high SS content is supplied to the dialysis machine without thorough pretreatment, the inlet distribution plate and hollow fiber bundles will be clogged with a large amount of SS in a short period of time, resulting in long-term problems. Unable to drive for a period of time. Therefore, in the filter press type, pretreatment consisting of coagulation sedimentation, sand filtration, and a 10 micron cut cartridge filter was performed to remove the SS content to 1 ppm or less. In the hollow fiber type, a 1 micron cut cartridge filter was further installed to perform the fourth treatment. Using the dialysate treated in this way, an acid recovery experiment was conducted using the same apparatus and under the same dialysis conditions as Nos. 1 to 6, and the changes in acid recovery rate and inlet pressure over time were investigated and are shown in Table 2.

【table】

[Table] Example 2 Stainless steel cleaning waste acid containing nitric acid and hydrofluoric acid contains 100 to 200 ppm of SS. The composition of the cleaning waste acid used in the experiment was 100 g of nitric acid and 15 g of boiling acid.
It is a mixed solution of g/g/. The dialysis method of the present invention was carried out on the washed waste acid using the same dialysis apparatus, dialysis conditions, and pretreatment conditions as in Example 1. As a result, the acid recovery rate in the diffusion liquid was as shown in Table 3.

【table】

[Table] The upper row of recovery rates shows nitric acid, and the lower row shows hydrofluoric acid. * indicates a comparative example.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams showing typical embodiments of the apparatus used in the present invention. In the figure, 1 is a vertical cylindrical container, 2 (and 2') is a tube plate, 3 (3' and 3'') is a partition, 4 is a tubular ion exchange membrane, 5 is a hole,
6 is a joint, 7, 8, 9, and 10 are supply ports or exhaust ports, 11 is an aeration tube, 12 is an aeration hole, and 13 is a gas outlet.

Claims (1)

[Claims] 1. A diffusion liquid or a dialysate is present inside an upright tubular ion exchange membrane, and a dialysate or a diffusion liquid is present outside the tubular ion exchange membrane, and the diffusion liquid and the dialysate flow countercurrently, and A diffusion dialysis method characterized by the presence of air bubbles in the dialysate.